Which combination of actions should the company take to meet these requirements?

Explanations:

Refactoring the application to serverless using AWS Lambda and .NET Core would require significant development changes, which contradicts the requirement to minimize changes. Additionally, AWS Lambda has limitations in terms of long-running processes and certain .NET functionalities.

Rehosting the application on AWS Elastic Beanstalk allows for minimal changes since it supports .NET applications and provides a Multi-AZ deployment option for high availability. This approach allows the company to leverage AWS infrastructure while maintaining the existing application architecture.

Replatforming the application to run on Amazon EC2 with an Amazon Linux AMI is not suitable because it may require more development changes to adapt the .NET application to run on Linux. The focus is on maintaining the current environment and minimizing changes, which this option does not fulfill.

Migrating from Oracle to Amazon DynamoDB is a significant change in the database type and structure. This option does not meet the requirement to minimize development changes as it involves moving to a completely different database model (NoSQL) and would require substantial application modifications.

Using AWS Database Migration Service (AWS DMS) to migrate the Oracle database to Oracle on Amazon RDS in a Multi-AZ deployment allows for a seamless transition to a managed database service while maintaining the same database technology. This option supports high availability and minimizes the need for application changes.